A conveyor is used widely at a factory and a physical distribution warehouse. The conveyor includes a roller conveyor which carries a transport object by a rotating roller, a roller conveyor which carries a transport object by an end-less belt, and a chain which carries a transport object by bucket and the like attached to the chain.
Patent Documents 1 to 3 and so on are known as a conventional art which relates to a conveyor. Patent Document 1 relates to trouble diagnosis of a conveyor from change in an electric current value of a motor by sensing the electric current value of a drive motor one by one. Patent Document 2 relates to trouble diagnosis of a conveyor from change in a rotation speed of the motor. Patent Document 3 relates to trouble diagnosis by sensing a belt slip with an electric current value in the conveyor belt.
Moreover, Patent Document 4 relates to a device which has a weight measuring part (weighing part) of a transport object, the device inspecting the transport object and automatically correcting a decreased speed of the conveyor, and the decreased speed being estimated from measured weight. Furthermore, Patent Document 4 discloses a technology to increase accuracy of weight measurement using a conveyor, wherein the conveyor has an approach run part provided behind the measuring part (upstream side based on the measuring part in conveying direction) and an object sensing device provided ahead of the approach run part (downstream side based on the approach run part in conveying direction), and wherein the conveyor includes measuring a required time from passing through the approach run part to reaching the object sensing device of the transport object and modifying the result obtained in the weight measuring part by using the required time.
However, these conventional technologies include a trouble diagnosis by a change in the electric current value or a rotation speed, or need to have a weight measuring part (weighing part) as described above.